Thin film transistor device with advanced characteristics by improved matching between a glass substrate and a silicon nitride layer

ABSTRACT

A thin film semiconductor device including an insulating substrate; and a structure provided on the insulating substrate and including a silicon layer containing hydrogen diffused therein and a silicon nitride layer. The insulating substrate is formed of an insulating material having a thermal expansion coefficient of 2.6x10-6 deg-1 or more or having a distortion point of 850 DEG  C. or lower.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thin film semiconductor device suchas a thin film transistor device, for use in a liquid crystal displaydevice, an image sensor and the like, which is produced at a lowtemperature, and a method for producing such a thin film semiconductordevice.

2. Description of the Related Art

In conventional field effect transistors including an active layerformed of polysilicon, microcrystalline silicon or noncrystallinesilicon, a great number of trapping levels and/or surface states arecaused by defects in the active layer. The existence of such a greatnumber of trapping levels and/or surface states lowers the mobility ofelectrons and holes and thus the threshold voltage fluctuates. In orderto solve such problems, a so-called "hydrogen passivation method" hasbeen used, by which the defects in the active layer are reduced byhydrogen, thereby lowering the number of defects in an area unit.

As a hydrogen passivation method, the following three methods have beenproposed:

(1) Exposing the structure including an active layer to hydrogen plasmaat a substrate temperature of 300° C. to 400° C., thereby introducinghydrogen into the active layer (hereinafter, referred to as the"hydrogen plasma method");

(2) Implanting hydrogen ions into the active layer and then annealingthe structure including an active layer (hereinafter, referred to as the"hydrogen ion implantation method"); and

(3) Coating the structure including an active layer with silicon nitrideincluding hydrogen (hereinafter, referred to as SiN:H) and thenannealing the structure, thereby diffusing hydrogen from the siliconnitride layer into the active layer.

According to the hydrogen plasma method or the hydrogen ion implantationmethod, damage to the active layer cannot be avoided when the hydrogenis introduced or implanted into the active layer. Further, especially inthe case where a planar transistor having a gate electrode formed of asilicon material is produced by the hydrogen plasma method, the speed ofhydrogen passivation is low, and thus there is a problem in terms ofthroughput.

Under these circumstances, the method of diffusing hydrogen in the SiN:Hlayer into the active layer by heating is considered to be advantageousas a hydrogen passivation method. Generally in the case of a thin filmtransistor including a substrate formed of silicon, hydrogen passivationachieves great effects when a SiN:H having a sufficient compressivestress during the passivation anneal is used (G. P. Pollack et al.,"Hydrogen Passivation of Polysilicon MOSFET's from a Plasma NitrideSource", IEEE Electron Devices Lett. vol. EDL-5, No. 11, November,1984). By contrast, in the case of a transistor having an insulatingsubstrate formed of a material such as quartz, hydrogen passivation doesnot realize sufficient improvement of transistor characteristics even byuse of the above-mentioned SiN:H.

SUMMARY OF THE INVENTION

A thin film semiconductor device according to the present inventionincludes an insulating substrate; and a structure provided on theinsulating substrate and including a silicon layer containing hydrogendiffused therein and a silicon nitride layer. The insulating substrateis formed of an insulating material having a thermal expansioncoefficient of 2.6×10⁻⁶ deg⁻¹ or more.

In one embodiment of the invention, the insulating substrate is formedof aluminoborosilicate glass.

Alternatively, a thin film semiconductor device according to the presentinvention includes an insulating substrate; and a structure provided onthe insulating substrate and including a silicon layer containinghydrogen diffused therein and a silicon nitride layer. The insulatingsubstrate is formed of an insulating material having a distortion pointof 850° C. or lower.

In one embodiment of the invention, the insulating substrate is formedof aluminoborosilicate glass.

Alternatively, a method for producing a thin film semiconductor deviceaccording to the present invention includes the steps of forming asilicon layer above a substrate formed of an insulating material havinga thermal expansion coefficient of 2.6×10⁻⁶ deg⁻¹ or more; forming asilicon nitride layer containing hydrogen above the silicon layer; andheating the silicon nitride layer, thereby diffusing the hydrogen intothe silicon layer.

In one embodiment of the invention, the silicon nitride layer is heatedat a temperature in the range of 400° C. to 550° C.

In one embodiment of the invention, the silicon nitride layer is formedby a plasma CVD method using a gas containing SiH₄ and NH₃ mixedtherein.

Alternatively, a method for producing a thin film semiconductor deviceaccording to the present invention includes the steps of forming asilicon layer above a substrate formed of an insulating material havinga distortion point of 850° C. or lower; forming a silicon nitride layercontaining hydrogen above the silicon layer; and heating the siliconnitride layer, thereby diffusing the hydrogen into the silicon layer.

In one embodiment of the invention, the silicon nitride layer is heatedat a temperature in the range of 400° C. to 550° C.

In one embodiment of the invention, the silicon nitride layer is formedby plasma CVD method using a gas containing SiH₄ and NH₃ mixed therein.

Thus, the invention described herein makes possible the advantages ofproviding a method for producing a thin film semiconductor device, bywhich satisfactory transistor characteristics are indicated in a shortperiod of time after hydrogen passivation starts, and a thin filmsemiconductor device produced by such a method.

These and other advantages of the present invention will become apparentto those skilled in the art upon reading and understanding the followingdetailed description with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a thin film transistor in a first exampleaccording to the present invention.

FIGS. 2a through 2g are cross sectional views taken across line a--a' ofFIG. 1, illustrating a method for producing the thin film transistorshown in FIG. 1.

FIG. 3 is a graph illustrating the relationship between the mobility ofcarriers obtained by applying an electric field and the time duration ofthe hydrogen diffusing annealing, concerning a thin film transistor inthe first example according to the present invention and a thin filmtransistor as a comparative example.

FIG. 4 is a graph illustrating the dependency of the threshold voltageon the time duration of the hydrogen diffusing annealing, concerning thethin film transistor in the first example according to the presentinvention and a thin film transistor as the comparative example.

FIG. 5 is a graph illustrating the dependency of the drain current onthe gate voltage, concerning the thin film transistor in the firstexample according to the present invention.

FIG. 6 is a graph illustrating the dependency of the drain current onthe gate voltage, concerning a thin film transistor as the comparativeexample.

FIG. 7 is a plan view of a thin film transistor in a second exampleaccording to the present invention.

FIGS. 8a through 8g are cross sectional views taken across line b--b' ofFIG. 7, illustrating a method for producing the thin film transistorshown in FIG. 7.

FIG. 9 is a graph illustrating the dependency of the threshold voltageon the time duration of the hydrogen diffusing annealing, concerningthin film transistors in the second example according to the presentinvention and thin film transistors as comparative examples.

FIG. 10 is a graph illustrating the relationship between the thermalexpansion coefficient of the substrate and the threshold voltageobtained after the hydrogen diffusing annealing is performed for 0.5hours, concerning the thin film transistors in the second exampleaccording to the present invention and the thin film transistors ascomparative the examples.

FIG. 11 is a graph illustrating a diffusion state of hydrogen in aregion formed of polysilicon with added P ions of the thin filmtransistor in the second example according to the present inventionafter the hydrogen diffusing annealing is performed for 0.5 hours.

FIG. 12 is a graph illustrating the dependency of the drain current onthe gate voltage concerning the thin film transistor having a substrateformed of glass A in the second example according to the presentinvention having.

FIG. 13 is a graph illustrating the dependency of the drain current onthe gate voltage concerning the thin film transistor having a substrateformed of quartz as the comparative example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described by way ofillustrating examples with reference to the accompanying drawings.

EXAMPLE 1

FIG. 1 is a plan view of a thin film transistor in a first exampleaccording to the present invention. FIGS. 2a through 2g are crosssectional views taken across line a--a' of FIG. 1, illustrating a methodfor producing the thin film transistor shown in FIG. 1.

A substrate 1 formed of aluminoborosilicate glass having a distortionpoint of 670° C. and a thermal expansion coefficient of 4×10⁻⁶ deg⁻¹ iswashed, and then a silicon dioxide layer 2 is formed in a thickness ofapproximately 500 nm on the substrate 1 in a atmospheric-pressure CVDapparatus as is shown in FIG. 2a. The resultant structure is annealedfor approximately 12 hours in an inert gas atmosphere, thereby raisingthe density of the silicon dioxide layer 2.

In a plasma CVD apparatus, SiH₄ is decomposed in plasma with theassistance of heat at a substrate temperature of 450° C., therebyforming a noncrystalline silicon film in a thickness of approximately100 nm on the silicon dioxide layer 3. The resultant structure is thenannealed at 600° C. for approximately 24 hours in an inert gasatmosphere, and thus turned into a polysilicon film. The polysiliconfilm is then patterned by photolithography to be a polysilicon layer 3having a pattern of islands as is shown in FIG. 2b.

A silicon dioxide film is formed in a thickness of approximately 100 nmso as to cover the polysilicon layer 3 in a atmospheric-pressure CVDapparatus. The resultant structure is then annealed for approximately 12hours in an inert gas atmosphere, thereby raising the density thereof.The resultant silicon dioxide film shown in FIG. 2c acts as a gateinsulating film 4.

A polysilicon film is formed in a thickness of approximately 300 nm onthe gate insulating film 4 in a low pressure CVD apparatus, and thenpatterned as specified by photolithography, thereby obtaining a gateelectrode 5 as is shown in FIG. 2d.

As is shown in FIG. 2e, phosphorus P ions are implanted into theresultant structure through a whole upper surface thereof in an amountof approximately 2×10¹⁵ ions/cm², and annealing is performed at 600° C.for approximately 20 hours. Thus, the resistances of the gate electrode5 and portions 6a and 6b of the polysilicon layer 3 are lowered, theportions 6a and 6b acting as a source and a drain, respectively.

As is shown in FIGS. 2f and 1, contact holes 7 and formed in the gateinsulating film 4 for connecting both the source 6a and the drain 6bwith and aluminum electrode 8 to be formed on the gate insulating film4. The aluminum electrode 8 is formed in a thickness of approximately300 nm so as to cover the gate electrode 5 and then patterned asspecified by photolithography. The resultant structure is annealed at440° C. for approximately 30 minutes to obtain ohmic contact between thegate electrode 5 and the aluminum electrode 8, between the source 6a andthe aluminum electrode 8, and between the drain 6b and the aluminumelectrode 8.

A gas containing SiH₄ and NH₃ mixed therein is decomposed by plasma at asubstrate temperature of 300° C., thereby forming a silicon nitridelayer 9 in a thickness of approximately 400 nm on the aluminum electrode8 by a plasma CVD method as is shown in FIGS. 2g and 1. The siliconnitride layer 9 contains hydrogen in an atomic percent of 1% to 30%.Contact holes 10 are formed in the silicon nitride layer 9 forelectrically connecting the aluminum electrode 8 and a conductive layerto be formed thereon (nor shown). The resultant structure is annealed ata temperature in the range of 400° C. to 550° C., thereby diffusinghydrogen in the silicon nitride layer 9 in to the polysilicon layer 3and the gate electrode 5 which act as an active layer in combination.Such annealing will be referred to as "hydrogen diffusing annealing".Thus, the thin film transistor shown in FIG. 1 is produced.

As a comparative example, another thin film transistor is produced in anidentical manner as described above except that quartz is used for asubstrate. The quartz used for the substrate has a distortion point of1000° C. and a thermal expansion coefficient of 5×10⁻⁷ deg⁻¹.

FIGS. 3 through 6 shown characteristics of the thin film transistor inthe first example according to the present invention and the thin filmtransistor as the comparative example having a substrate formed ofquartz. Both of the thin film transistors were produced in an identicalmanner in which the hydrogen diffusing annealing was performed at 440°C.

FIG. 3 shows the relationship between the mobility of carriers obtainedby applying an electric field and the time duration of the hydrogendiffusing annealing. FIG. 4 shows the dependency of the thresholdvoltage on the time duration of the hydrogen diffusing annealing. Ineach of FIGS. 3 and 4, the solid line corresponds to the thin filmtransistor according to the present invention, and the dashed linecorresponds to the thin film transistor as the comparative example. FIG.5 shows the dependency of the drain current on the gate voltageconcerning the thin film transistor according to the present invention,and FIG. 6 shows such dependency concerning the thin film transistor asthe comparative example. Each thin film transistor has a channel lengthof 5 μm, a channel width of 50 μm, and a voltage between the drain 6band the source 6a of 0.5 V. Each transistor is obtained after performinghydrogen diffusing annealing for 8 hours.

It is apparent from FIG. 3 that the mobility of the thin film transistoraccording to the present invention reaches a saturation state after thehydrogen diffusing annealing is performed for 60 minutes, whereas 120minutes are necessary until the mobility of the thin film transistor asthe comparative example reaches a saturation state. Further, after thehydrogen diffusing annealing is performed for 8 hours, the mobility ofthe thin film transistor according to the present invention is 29.1 cm²/V·s, whereas that of the thin film transistor as the comparativeexample is only 23.4 cm² /V·s.

FIG. 4 shows that the threshold voltage reaches a saturation state afterthe hydrogen diffusing annealing is performed for 120 minutes with bothof the thin film transistors. However, after the hydrogen diffusingannealing is performed for 8 hours, the threshold voltage of the thinfilm transistor according to the present invention is 12.0 V, whereasthat of the thin film transistor as the comparative example is 14.2 V.

As is apparent from FIGS. 3 through 6, in the thin film transistor inthe first example according to the present invention having a substrateformed of aluminoborosilicate glass, the mobility by the electric fieldreaches a saturation state in a shorter period of time, and bettercharacteristics are indicated after saturation than the thin filmtransistor having a substrate formed of quartz.

EXAMPLE 2

FIG. 7 is a plan view of a thin film transistor in a second exampleaccording to the present invention. FIGS. 8a through 8g are crosssectional views taken across line b--b' of FIG. 7, illustrating a methodfor producing the thin film transistor shown in FIG. 7.

In the second example, three types of thin film transistors respectivelyincluding substrates 11 formed of three types of glass A, B, and C areformed. The three types of glass A, B and C each have a high distortionpoint and a thermal expansion coefficient of more than 2.6×10⁻⁶ deg⁻¹ asis shown later in Table 1. Since these thin film transistors areidentical except for the type of glass, the production method will bedescribed only once.

The substrate 11 formed of any one of the above-described glass types iswashed, and then a silicon dioxide layer 12 is formed in a thickness ofapproximately 500 nm on the substrate 11 in a atmospheric-pressure CVDapparatus as is shown in FIG. 8a. The resultant structure is annealedfor approximately 12 hours in an inert gas atmosphere, thereby raisingthe density of the silicon dioxide layer 12.

In a low pressure CVD apparatus, Si₂ H₆ is decomposed by heat at asubstrate temperature of 450° C., thereby forming a noncrystallinesilicon film in a thickness of approximately 100 nm on the silicondioxide layer 12. The resultant structure is then annealed at 600° C.for approximately 24 hours in an inert gas atmosphere, and thus turnedinto a polysilicon film. The polysilicon film is then patterned byphotolithography, thereby forming a polysilicon layer 13 having apattern of islands as is shown in FIG. 8b.

A silicon dioxide film is formed in a thickness of approximately 100 nmso as to cover the polysilicon layer 13 in a atmospheric-pressure CVDapparatus. The resultant structure is annealed for approximately 12hours in an inert gas atmosphere, thereby raising the density thereof.The resultant silicon dioxide film shown in FIG. 8c acts as a gateinsulating film 14.

A polysilicon film is formed in a thickness of approximately 300 nm onthe gate insulating film 14 in a low pressure CVD apparatus, and thenpatterned as specified by photolithography, thereby obtaining a gateelectrode 15 as is shown in FIG. 8d.

As is shown in FIG. 8e, P ions are implanted into the resultantstructure through the whole upper surface thereof in an amount ofapproximately 2×10¹⁵ ions/cm₂, and annealing is performed at 600° C. forapproximately 20 hours. Thus, the resistances of the gate electrode 15and portions 16a and 16b of the polysilicon layer 13 are lowered, theportions 16a and 16b acting as a source and a drain, respectively.

As is shown in FIGS. 8f and 7, contact holes 17 are formed in the gateinsulating film 14 for connecting both of the source 16a and the drain16b with an aluminum electrode 18 to be formed on the gate insulatingfilm 14. The aluminum electrode 18 is formed in a thickness ofapproximately 300 nm so as to cover the gate electrode 15 and thenpatterned as specified by photolithography. The resultant structure isannealed at 440° C. for approximately 30 minutes to obtain ohmic contactbetween the gate electrode 15 and the aluminum electrode 18, between thesource 16a and the aluminum electrode 18, and between the drain 16b andthe aluminum electrode 18.

A gas containing SiH₄ and NH₃ mixed therein is decomposed by plasma at asubstrate temperature of 300° C., thereby forming a silicon nitridelayer 19 in a thickness of approximately 400 nm by a plasma CVD methodas is shown in FIGS. 8g and 7. The silicon nitride layer 19 containshydrogen in an atomic percent of 1% and 30%. The resultant structure isannealed at a temperature in the range of 400° C. to 550° C., therebydiffusing hydrogen in the silicon nitride layer 19 into the polysiliconlayer 13 and the gate electrode 15 which act as an active layer incombination. Such annealing will be referred to as "hydrogen diffusingannealing". Contact holes 20 are formed in the silicon nitride layer 19for electrically connecting the aluminum electrode 18 and a conductivelayer to be formed thereon (not shown). Thus, the thin film transistorshown in FIG. 7 is produced.

As comparative examples, thin film transistors are produced in anidentical manner as described above except that quartz and crystalsilicon are used for substrates thereof, respectively. The quartz usedfor the substrate has a distortion point of 1000° C. and a thermalexpansion coefficient of 5×10⁻⁷ deg ⁻¹.

FIGS. 9 through 13 show characteristics of the thin film transistors inthe second example according to the present invention and the thin filmtransistors as the comparative examples having substrates formed ofquartz and silicon. As is mentioned above, the thin film transistors inthe second example respectively include substrates formed of glass typesA, B and C. All of the thin film transistors were produced in anidentical manner in which the hydrogen diffusing annealing was performedat 490° C.

FIG. 9 shows the dependency of the threshold voltage on the timeduration of the hydrogen diffusing annealing, concerning the thin filmtransistors in the second example according to the present invention andthe thin film transistors as comparative examples. FIG. 10 shows therelationship between the thermal expansion coefficient of the substrateand the threshold voltage obtained after the hydrogen diffusingannealing is performed for 0.5 hour, concerning the thin film transistorin the second example and the thin film transistors as the comparativeexamples. FIG. 11 shows a diffusion state of hydrogen in the regionformed of polysilicon added with P ions of the thin film transistor inthe second example after the hydrogen diffusing annealing is performedfor 0.5 hour. FIG. 12 shows the dependency of the drain current on thegate voltage concerning the thin film transistor having a substrateformed of glass A in the second example of the present invention, andFIG. 13 shows such dependency of the thin film transistor having asubstrate formed of quartz as the comparative example. Each thin filmtransistor has a channel length of 50 μm, a channel width of 50 μm, anda voltage between the drain 16b and the source 16a of 0.5 V. Eachtransistor is obtained after performing the hydrogen diffusing annealingfor 0.5 hour. As is mentioned above, Table 1 shows the thermal expansioncoefficient of the three types of glass A, B, and C used for the thinfilm transistors in the second example and also quartz and crystalsilicon used for the thin film transistors as comparative examples.

                  TABLE 1                                                         ______________________________________                                                     Thermal expansion coefficient                                    Substrate    (×10.sup.-7 deg.sup.-1)                                    ______________________________________                                        Glass A      42                                                               Glass B      37                                                               Glass C      49                                                               Quartz       6                                                                Crystal Silicon                                                                            26                                                               ______________________________________                                    

It is apparent from FIGS. 9 through 13 that, in the thin filmtransistors in the second example according to the present inventionincluding a substrate having a thermal expansion coefficient of 2.6×10⁻⁶deg⁻¹ or more, satisfactory characteristics can be obtained in a shorterperiod of time of hydrogen diffusing annealing than in the thin filmtransistor including a substrate having a thermal expansion coefficientof less than 2.6×10⁻⁶ deg⁻¹. Further, it is apparent from FIG. 11 thatthe difference in the characteristics depending on the type of substrateis caused by the difference in the speed for supplying hydrogen in theSiN:H layer to the active layer.

In the thin film transistor having a substrate formed of quartz,sufficiently good characteristics are not obtained even by hydrogenpassivation in which hydrogen is diffused from the SiN:H layer into theactive layer by heating. The following is considered to be one reasonfor this: While the annealing is performed by heating in order todiffuse hydrogen in the SiN:H layer to the active layer, defects such asvoids are generated in the SiN:H layer. Hydrogen molecules are caught inthe voids, and thus the ratio of hydrogen molecules introduced into theactive layer is low.

The stress of the SiN:H layer depends on various parameters of layerformation. Generally, a SiN:H layer having a compressive stress withrespect to a crystal silicon substrate (thermal expansion coefficient:2.6×10⁻⁶ deg⁻¹) at room temperature is hydrogenated at a higherefficiency than a SiN:H layer having a tensile stress at roomtemperature. This is because the former SiN:H layer traps hydrogenmolecules at a higher efficiency, and thus allows the hydrogen moleculesto be discharged into the atmosphere at a lower ratio than from thelatter SiN:H layer.

For example, in the case where a substrate formed of quartz having athermal expansion coefficient of approximately 5×10⁻⁷ deg⁻¹ is used, theSiN:H layer has a higher tensile stress with respect to such a substratethan with respect to a silicon substrate at room temperature. However,the hydrogen diffusing annealing is usually performed at a temperaturein the range of 400° C. to 550° C. In such a temperature range, theSiN:H layer has a higher compressive stress than at room temperature.This phenomenon causes defects such as voids in the SiN:H layer andpeeling-off of the SiN:H layer.

By contrast, an insulating substrate having a distortion point of 850°C. or lower has a thermal expansion coefficient of 3×10⁻⁶ deg⁻¹ to6×10⁻⁶ deg⁻¹. When such a substrate is used, the SiN:H layer has asubstantially identical tensile stress with the case where a siliconsubstrate is used, or has a compressive stress, at room temperature.After the hydrogen diffusing annealing, the SiN:H layer still keeps thesame tensile stress with that at room temperature or has a highertensile stress. Accordingly, as long as no void is generated or nopeeling-off occurs at room temperature, there is no problem in diffusinghydrogen to the active layer by heating. As a result, excellentcharacteristics can be obtained in a short period of time after hydrogenpassivation starts.

Even in the case of a thin film transistor including a substrate havinga thermal expansion coefficient of 2.6×10⁻⁶ deg⁻¹ or more, hydrogen inthe SiN:H layer is supplied to the active layer faster, and thus themobility of carriers in the transistor reaches a saturation state in ashorter period of time than a thin film transistor including a substratehaving a thermal expansion coefficient of less than 2.6×10⁻⁶ deg⁻¹.

As has been described so far, according to the present invention, by useof a glass substrate having a distortion point of 850° C. or lower in athin film transistor, generation of defects such as voids in the SiN:Hlayer, occurrence of peeling-off of a SiN:H layer, and otherinconveniences are prevented during hydrogen diffusing annealing. As aresult, satisfactory transistor characteristics can be obtained in ashort period of time after start of the hydrogen passivation in whichhydrogen in the SiN:H layer is diffused into an active layer.

Further, by the use of a substrate having a thermal expansioncoefficient of 2.6×10⁻⁶ deg⁻¹ or more, satisfactory transistorcharacteristics can be attained in a short period of time after start ofhydrogen passivation.

Various other modifications will be apparent to and can be readily madeby those skilled in the art without departing from the scope and spiritof this invention. Accordingly, it is not intended that the scope of theclaims appended hereto be limited to the description as set forthherein, but rather that the claims be broadly construed.

What is claimed is:
 1. A thin film semiconductor device, comprising:aninsulating substrate formed of an insulating material having a thermalexpansion coefficient of 2.6×10⁻⁶ deg.⁻¹ or more, a thin film transistorprovided on the insulating substrate, the thin film transistor includinga silicon layer as an active layer; and a silicon nitride layer formedon the silicon layer, the silicon nitride layer including hydrogen,wherein the silicon layer is passivated with hydrogen diffused from thesilicon nitride layer by annealing the silicon nitride layer.
 2. A thinfilm semiconductor device according to claim 1, wherein the insulatingsubstrate is formed of aluminoborosilicate glass.
 3. A thin filmsemiconductor device according to claim 2, wherein the insulatingsubstrate of aluminoborosilicate glass has a thermal expansioncoefficient of 4×10⁻⁶ deg.⁻¹, the silicon layer is a polysilicon layerand the silicon nitride layer has a compressive stress.
 4. A thin filmsemiconductor device according to claim 1, wherein the silicon layer isformed of polysilicon.
 5. A thin film device according to claim 1,wherein the insulating substrate is formed of glass.
 6. A thin filmsemiconductor device according to claim 1, wherein the silicon nitridelayer has compressive stress.
 7. A thin film semiconductor deviceaccording to claim 1, wherein the hydrogen in the silicon nitride layeris present in an atomic percent of 1% to 30%.
 8. A thin filmsemiconductor device, comprising:an insulating substrate formed of aninsulating material having a distortion point of 850° C. or lower, athin film transistor provided on the insulating substrate, the thin filmtransistor including a silicon layer as an active layer; and a siliconnitride layer formed on the silicon layer, the silicon nitride layerincluding hydrogen, wherein the silicon layer is passivated withhydrogen diffused from the silicon nitride layer by annealing thesilicone nitride layer.
 9. A thin film semiconductor device according toclaim 8, wherein the insulating substrate is formed ofaluminoborosilicate glass.
 10. A thin film semiconductor deviceaccording to claim 9, wherein the insulating substrate ofaluminoborosilicate glass has a distortion point of 670° C., the siliconlayer is a polysilicon layer and the silicon nitride layer has acompressive stress.
 11. A thin film semiconductor device according toclaim 8, wherein the silicon layer is formed of polysilicon.
 12. A thinfilm device according to claim 8, wherein the insulating substrate isformed of glass.
 13. A thin film semiconductor device according to claim8, wherein the silicon nitride layer has compressive stress.
 14. A thinfilm semiconductor device according to claim 8, wherein the hydrogen inthe silicon nitride layer is present in an atomic percent of 1% to 30%.